Conventional light transmission systems used for vehicle head lights or tail lights typically use a bulb and reflector system. In a bulb and reflector system, the filament of the bulb is placed at or near a focal point of a parabolic reflector. The light emitted by the bulb filament is collected by the reflector and reflected outward to form a light beam. A lens is used to shape the light beam into a specified pattern to satisfy vehicle lighting specifications. Typically, in an automotive application, a conventional bulb and reflector system collects and reflects only thirty percent of the light emitted from the bulb filament into the useful lighting area.
Bulb and reflector systems have several disadvantages, including aerodynamics and aesthetic styling. For example, the depth of the reflector along its focal axis and the height of the reflector in directions perpendicular to the focal axis greatly limit attempts at streamlining vehicle contours. Additionally, thermal energy given off by the bulb during operation must be considered. The size of the reflector as well as the material used in its construction vary depending upon the amount of thermal energy generated by the bulb filament. Decreasing the size of the reflector requires use of materials with high thermal resistivity.
One approach to develop an automotive lighting system for use with newer streamlined body designs is proposed in U.S. Pat. No. 5,434,754, assigned to the assignee of the present invention, which discloses the combination of a fiber optic light guide which transmits light from a remote light source, through a light manifold, and to a reflector. One problem with such an approach is the necessity for a manifold. A manifold is required to expand the incoming light for distribution across the lamp surface. This results in a substantial portion of unlit area required for the manifold and hence a larger footprint of the overall lamp. This creates vehicle lighting design inflexibility.
A laser illuminated thin sheet optical element lighting device as disclosed in application Ser. No. 08/780,034 entitled Laser Illuminated Lighting System, assigned to the assignee of the present invention, addressed a number of deficiencies in the vehicle lighting arts. However, the problem of having a large amount of unlit area required for the manifold portion still remains.
Therefore, it would be desirable to provide a laser illuminated, thin sheet optic lighting system for a vehicle which accommodates manufacturing and thermal considerations as well as the space limitations dictated by vehicular aerodynamic and styling requirements.